Battery systems, in particular Li-ion battery systems, are often used as energy storage devices for a drive motor in hybrid or electric vehicles. Known Li-ion battery systems comprise a plurality of Li-ion battery cells that are electrically connected to one another in series and/or in parallel. In order to ensure operational safety, battery systems of this type comprise a battery management system by means of which it is possible to monitor the battery cells or parameters of the battery cells, such as voltages, currents and charges.
In order to ensure an optimum performance and to ensure that the battery cells age as little as possible and to ensure a high degree of operational safety, it has been proven to monitor temperatures of battery systems and thus to be able to control in a closed-loop manner the operation of the battery system within a predetermined temperature range. In so doing, it is important to monitor the temperature of the individual battery cells. On the basis of the determined temperatures of the battery cells, it is possible to control in a closed-loop manner by way of example a cooling device for cooling the battery cells to an optimum working temperature. Moreover, the determined temperatures may be provided to the battery management system for predicting the performance of the battery cells on the basis of temperature-dependent battery cell parameters, such as by way of example internal resistances or current limits. Finally, due to the high chemical activity of lithium, it is particularly important in the case of Li-ion battery cells in order to ensure operational safety that the battery cells do not exceed a predetermined maximum temperature since the explosion risk is increased above the maximum temperature.
In practice, it has proven so as to reduce costs in the case of battery systems having a multiplicity of battery cells to monitor the temperature of only a few battery cells or at a few measuring sites in the battery system by means of temperature sensors. Accordingly, a good thermal connection of the temperature sensor to the measuring site and also an electrical coupling to the battery management system is to be taken into consideration for the integration of a temperature sensor in the battery system. It is possible to produce a thermal connection by way of example by means of mechanically pressing the temperature sensor against the measuring site or by means of attaching said temperature sensor for example by means of a soldering procedure, a welding procedure, screws or an adhesion procedure. In order to produce the electrical coupling, it is possible to use plug-in systems, to integrate flex-foils or to solder connection wires of the temperature sensor to the battery management system.
In the case of known battery systems, the procedure of integrating temperature sensors, in particular when producing an electrical coupling by means of a plug-in system, often incurs high costs. It is often necessary to perform a complex modification of the measuring site when mechanically connecting the temperature sensor to the measuring site, in particular when using screws, a soldering procedure or rivets. It is generally not possible in this case to provide a direct contact with the battery cell. Moreover, known temperature sensors are rigid or are essentially rigid with the result that it is necessary when integrating the temperature sensor to take into consideration even small deviations in a spacing between the measuring site and the site at which the temperature sensor is connected to the battery management system in order to ensure an optimum measurement of the temperature and by way of example to avoid a gap between the temperature sensor and the measuring site. Furthermore, battery systems are becoming increasingly more complex and often comprise a comparatively small installation space for temperature sensors with the result that it is necessary to use especially configured temperature sensors rather than those of a standard design. This likewise results in high production costs and also a high outlay with regard to the qualification expenses.